A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
1. Field of the Invention
The present invention generally relates to a method for manufacturing an electronic device such as a semiconductor integrated circuit device, a super conductive device, a micromachine, a TFT, or a wiring substrate. More particularly, the invention is related to a technique for manufacturing an electronic device that is effective in its application to a lithography technique used in a semiconductor integrated circuit device manufacturing process.
2. Discussion of Background
In the manufacture of a semiconductor integrated circuit device there is used a lithography technique as means for forming a fine pattern on a wafer. In the lithography technique there mainly is employed a projection exposure system. A pattern of a photomask (mask) attached to the projection exposure system is transferred onto the wafer to form a device pattern.
An ordinary mask is fabricated by patterning a metallic film having a light shielding property such as a film of chromium (Cr) formed on a transparent mask substrate, or by patterning an inorganic film having a light attenuating or shielding property such as a film of MoSi, ZrSiO, or SiN formed on a transparent mask substrate. That is, an ordinary mask includes the above metallic film or inorganic film formed in a desired shape on a transparent mask.
The aforesaid metallic film or inorganic film is usually formed by a sputtering method. For example, the metallic film is subjected to the following processing. First, a resist film is applied onto the metallic film and thereafter a desired pattern is written on the resist film by an electron beam exposure system or a laser writer. Subsequently, a resist pattern of a desired shape is formed by development. Then with the resist pattern is used as a masking layer. The metallic film is then patterned, for example, by dry etching or wet etching. Thereafter, the resist pattern is removed, followed by washing, etc., to form on a transparent substrate an opaque pattern of a desired shape mainly made of the metallic film. The mask using the inorganic film is also fabricated by the same process.
Unfortunately, the mask of this construction involves the problem that the number of manufacturing steps is large and that the cost therefore increases. With a view to simplifying the mask fabricating process and reducing the cost, for example, in JP-A No. 289307/1993 there is disclosed what is called a resist mask method in which an opaque element is formed by a resist film. This method utilizes such a property of an ordinary electron beam-sensitive resist film or a photosensitive resist film as shields vacuum ultraviolet light having a wavelength of not longer than 200 nm or so. According to this method, an opaque film etching step and a resist film removing step are not necessary, thus permitting reduction of the mask cost and shortening of turn around time (TAT) as a result of simplification of the process.
Recently, with competition in the development of semiconductor integrated circuit devices, it has become necessary to use plural sheets of mask because of the necessity of accelerating a device debug, and a quick fabrication of low-cost mask has been becoming more and more necessary. This requirement is increasing desirable under a recent increase in the demand for system LSIs which are manufactured in a wide variety, small lot production mode. Thus, there is an increased demand for quick mask fabrication and reduction of mask costs.
A phase shift method is known as a lithography technique for forming a fine pattern of submicron or smaller. One of the masks employed in this method uses a halftone phase shift mask. In this mask, a translucent film is disposed in a pattern opening to invert the phase of light passing between adjacent patterns, thereby enhancing the light intensity contrast of a transfer image. With this mask, it becomes possible to form a fine pattern of a sub-wavelength size on a wafer. The fabrication of this halftone mask requires a larger number of manufacturing steps than in the manufacture of an ordinary binary mask. Consequently, the cost of the mask is extremely high in comparison with the ordinary Cr mask. In an effort to eliminate such a drawback there has been proposed a halftone type resist mask in which a translucent phase film is formed by a photosensitive translucent film using resist to attain a further reduction of cost. This resist mask is disclosed, for example, in JP-A No. 324795/2001.
The resist mask is very effective in reducing cost and shortening TAT. Unfortunately, the resist film as an opaque element is formed of an organic material and is therefore apt to react with light used in exposure. Also, patterns tend to deform by repeated exposure to excimer laser beam, such as ArF or KrF.
It has been recognized that what is needed is solutions to such problems as the deterioration in accuracy of transfer patterns caused by the deformation in shape of resist patterns and changes in light absorption and phase difference during the fabrication of semiconductors. Broadly speaking, the present invention fills these needs by providing a method for manufacturing an electronic device. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device or a method. Several inventive embodiments of the present invention are described below.
According to one embodiment, a mask opaque element is formed using a resist comprised of a resin, the resin containing a IV group element such as silicon or germanium or an iodonium compound or a metal, whereby the problem of irradiation durability being insufficient and the pattern size varying with exposure is solved. Upon radiation of light onto a resist opaque pattern, reaction proceeds from a surface side and there occurred a decrease of film. Also, the surroundings of a mask in an exposure system are in the air and, consequently, active oxygen generated by the irradiation of such excimer laser beam as ArF or KrF causes a change in film thickness and a dimensional change.
In other words, a surface reaction of resist with etching occurs based on active oxygen as a main reaction. Accordingly, for protecting the resist as an organic matter from active oxygen, an IV group element such as silicon or germanium, or an iodonium compound, or a metal is incorporated in the resist to decrease the etching rate.
In another embodiment, a photosensitive, transparent Si-containing resist and an organic composition having sensitivity to excimer laser beam as exposure light are mixed together to adjust the transmittance. The resist thereby obtained is used as a translucent film to form a halftone mask. The adjustment of phase angle is conducted by adjusting the film thickness of a shield resist pattern.
There may be a fear that the organic composition used for adjusting both transmittance and phase may react upon irradiation of exposure light, resulting in both transmittance and phase being changed. With the Si-containing resist, however, it is possible to suppress the occurrence of a change in both transmittance and phase.
In still another embodiment, after a resist pattern is formed on the mask, a transparent organic film is formed on the pattern to further suppress the change in both transmittance and phase of the resist which is a halftone film.
The invention encompasses other embodiments of a method, an apparatus, and a computer-readable medium, which are configured as set forth above and with other features and alternatives.